Gas operating mechanism for an autoloading firearm



June 21, 1960 R. CRITTENDON ET AL 2,941,450

GAS OPERATING MECHANISM FOR AN AuToLoADING FIREARM 2 Sheets-Sheet lFiled May 2, 1956 Uflid Sta arent GAS OPERATING MECHANISM FOR AN AUTO-LOADING FIREARM Filed May 2, 1956, Ser. No. 582,153

3 Claims. (Cl. 89;-191) This invention relates to an autoloading firearmand more .particularly to an autoloading shotgun which may be producedin the various conventional shot shell gauges and which will be capablein any gauge of handling the diversity of various powered shot shellscommerciallly available.

There have been available for many years autoloading Shotguns whichdepend for their performance on utilization of the recoil motionimparted to a movably mounted barrel by the tiring of the shot shell.While such shotguns have enjoyed wide acceptance, they are expensive tomanufacture, for great care must be employed in their construction toinsure that the recoil movement of the barrel is accurately guided andthat the forces generated in stopping that recoil motion are adequatelyabsorbed. Further, the motion of the barrel and the consequentredistribution of the recoil forces are disturbing to some shooters.There have been attempts, as exemplified by U.S. Patent No. 2,482,880,to operate an autoloading shot gun by means of gas pressure derived fromthe shot shell propellant. Insofar as we are aware, such designs havenot been commercially acceptable and it is believed that diliiculty mayhave been found in adapting this principle to successful operation witha range of high-powered and low-powered shot shells with which acommercial design must be capable of operating.

It is the principal object of this invention to produce a fixed barrelautoloading shotgun which may be manufactured with greateconomy andwhich is capable of functioning with the Variety of high and low-poweredshot shells commercially available.

In order to accomplish this result, we propose to utilize to thegreatest possible extent complete assemblies and individual partscommercially available as parts of an existing fixed barrel manuallyoperated repeating shotgun; Such a manually operated shotgun isillustrated in U.S. Patent No. 2,645,873 and the -fire control assemblywhich is an importantcomponent thereof is illustrated in detail in U.S.Patent No. 2,675,638. We contemplate that this manually operated shotgunmay be best converted to autoloading operation by the utilization ofoperating power derived from two sources. One of these sources of poweris the excess energy contained in the charge of expanding gas whichforces the shot pellets through the barrel of the shotgun. We propose totapthis source of power -by providing a gas port communicating with thebarrel in the manner of the conventional gas operated rearm and to applythe gas thus diverted from the barrel to provide part of the forceneeded to operate the -autoloading mechanism. The other source of poweris that found in the inertia effects resulting from the recoil of the`gun as a w-hole and the stoppage of that recoil by the oppositionprovided by the shooters shoulder. By the proper utilization andproportioning of these two sources of power, we have been able toproduce an autoloading shotgun which, with a minimum of manualadjustment, functions adequately and dependably with the full range ofvarious powered shot shells com` 2,941,450 Patented June 21, 196)mercially available in the appropriate gauges, extending from therelatively low powered loads provided for trap shooting to the heaviesthunting loads. In l2 gauge, the range isfrom 2% to 4 dram equivalentpowder charge with l to ll/z ounces of shot.

The exact nature of the invention, including several refinements indetail as well as other objects and advantages thereof, will becomeapparent from consideration of the following specification, referring tothe attached drawings in which:

Fig. 1 is a longitudinal vertical sectional view through a shotgunproduced in accordance with our invention.

Fig. la is an enlarged fragment of Fig. l.

Fig. 2 is a vertical cross-sectional view on the line 2 2" of Fig. l,illustrating the attachment of the action bars to the gas piston.

Fig. 3 is a horizontal sectional view illustrating the attachment of theaction bars to the gas piston. It is taken on the line 3 3 of Fig. 1.

Fig. 4 is a vertical cross-sectional View taken on the line 4 4 of Fig1, illustrating the adjustments possible with the magazine cap.

Fig. 5 is a vertical cross-sectional view through the gas port portionof the mechanism taken on the line 5-5 of Fig. 1.

Fig. 6 is a fragmentary top plan view with the barrel, fore-end, andmagazine cap removed from the shutgun.

Referring tothe drawings, it will be seen that the shotgun illustratedtherein corresponds generally to that shown in U.S. Patent No. 2,645,873above referred to. it will be noted that the shotgun comprises areceiver 1 having a counterbore 2. in which'there is received a barrelextension 3 secured to or integral with a barrel 4. A t

magazine tube 5, which also functions at its forward end as a gascylinder, extends into the receiver in axial paral lelism with thebarrel and is rigidly secured to the receiveras by a furnace orinduction brazing operation. The magazine tube houses the usual magazinefollower 6 and follower spring 7, the latter abutting at its forward endagainst a magazine spring stop 8 secured in place by a crosspin 9 or acrimped impression in the magazine tube. A barrel guide'ring 10 issecured to the barrel 4 in position to embrace the forward or gascylinder end of the magazine tube when the barrel extension is seated inthe receiver. Assembly of the barrel to the receiver is maintained by amagazine cap 11, which threadably engages the magazine tube and bearsagainst'the forward housed in the barrel guide ring and engageablewithserrations 12 in the rear face of the magazine cap.y As the descriptionproceeds, it will become apparent that this construction permits takingdown the gun or replacing barrels without disturbance or disassembly ofthe gas cylinder, piston or other internal working parts.

A wooden fore-end 13 substantially encloses the magazine tube and closesthe gap between the magazine tube and the barrel 4. This wooden fore-endis secured in place by a resilient rubber-like fore-end ring washer 15engaged by the rear face of the barrel guide ring and urging a fore-endring 14 having an undercut conical rear face into secure engagement withan undercut forwardly facing abutment 16 formed in the Wood of thefore-end. At the rear end of the fore-end an angularly disposed tenon 17is received in a matching cut in the Within the receiver 1 a breech boltslide 18 is mounted for fore and aft reciprocation and guided by meanswhich will later be described. This slide 18 is provided withasubstantially rectangular lug 19 which is received within an aperture 20formed in the body of a breech bolt 21. As in the patent previouslyreferred to, a locking block 22 is also received in this aperture andhas the function of interlocking the breech bolt 21 with the barrelextension 3 through the medium of a locking lug 23 engaged with asuitably shaped recess in the barrel extension. An operating handle 24passes horizontally through a clearance aperture in the sidewall of thebreech bolt into engagement with the breech bolt slide and is therereleasably retained by means of a spring urged detent plunger 25.

As in the case of the prior patent above referred to, apair of actionbars 26 are provided which are slidable `in fore and aft grooves formedin the sidewalls of the receiver. The action bars are interlocked withthe breech bolt slide by means of lugs 27 on the actionbars engaged incut-outs in the side lianges of the breech bolt slide. By this means thebreech bolt slide and breech bolt are supported from the longiudinalguide grooves in the receiver walls and confined between the action barsand the top wall of the receiver. The action bars extend forwardly outof the receiver and continue in the space between the magazine tube andthe barrel to a point where they are joined by a connecting bridge 28formed integrally with the pair of action bars. A formed rivet 29 issecured to the connecting bridge 28 and passes through an elongated slot30 in themagazine tube 5 into engagement with la hole 31 formed in theskirt 32a assembled in unitary fashion with a gas piston 32. The gaspiston 32 is slidably received in the forward or gas cylinder end of themagazine tube and is urged to a forward position therein by the forceapplied by a breech closing spring 33, also housed within the magazinetube and engaged at its rear end against the spring stop 8. The actionbars are preferably slender, resilient memb ers capable of exingsuiciently to aid in smoothing out any peaks in the forces transmittedfrom the gas piston to the breech bolt slide. v

. Propellent powder gas s tapped from the barrel 4 through a pair of gasports 34 drilled forwardly and upwardly through 'the barrel guide ringto intersect at an v acute angle with the bore of the barrel. With themechanism in the assembled position, the gas ports 34 communicate withmatching gas ports 35 in the wall of the gas cylinder end of themagazine tube and, with the gas piston in its foremost position, thesetwo pre1V viously mentioned gas ports communicate with gas ports 36formed in the skirt 32a of the gas piston 32. The ports 36 are duplexedas best seen in Fig. 6 so that the ports 35 remain in communication withthe interior of the gas piston after movement of the piston. By thismeans, propellent powder gases from the bore of the barrel are appliedto the space within the gas piston end, expanding within the chamberprovided between the gas piston and the magazine cap, act upon thepiston to move the piston rearwardly to operate the breech bolt slideand mechanism associated therewith. As will be noteda small gas vent 37and threee larger gasvents 38 are provided in the magazine cap. Throughmanipulation of the selector dial 39 which is rotatably mounted on themagazine cap and provided with apertures 40, either the small vent 37 orall three of the larger vents 38 may be placed in communication with theatmosphere to provide a selected degree of gas escape from the magazinetube or gas cylinder. This arrange ment permits a portion of the gasadmitted to the magazine tube to be bled out to atmosphere withimportant advantages in maintaining the cleanliness of the system aswell as in improved functioning. Since this escape of gas is through themagazine cap rather than inside the fore-end, it does not tend to splitor otherwise weaken the fore-end which does not therefore requireinternal reinforcement with a steel sleeve.

Within the receiver 1 there is mounted a trigger plate 4l correspondingsubstantially to that shown in both of the Patents Nos. 2,645,873 and2,675,638, previously referred to. This fire control assembly differsfrom that shown in the iirst-mentioned prior patents only in that thedisconnector 42 is so formed at itsv forward end that it does not act asan action bar lock but is, instead, overridden by the angular rear end43 on one of the action bars and downwardly displaced thereby wheneverthe action bar is rearwardly displaced by any substantial amount fromits forward or breech locked position.. The result of this overriding ofthe disconnector is to disable the tire control mechanism and make itimpossible to release the hammer unless the breech is closed andsecurely locked 'to the barrel extension 3. By reference to either ofthe cited patents, it can be noted that the tire control mechanism is adisconnector type of lire control which does not permit the trigger -toreassume control of the hammer after firing ashot unless or until thetrigger finger is completely relaxed to allowthe trigger to return toits forward position. In this way, it is possible to prevent fullautomatic tire, as in a machine gun.

As previously noted, the autoloading operation of this firearm isdependent on the use of power derived from two sources. Considering rst,the power derived from the inertia eects, it will be noted that thesystem comprising the breech bolt 21, the locking block 22, the breechbolt slide 19, the dual action bars 26, and the gas piston 32, is oneinvolving parts of substantial weight and inertia. In typical 12, 16,and 20 gauge embodiments of our invention the breech bolt slide 19, dualaction bars 26 and gas piston 32, which is the portion of the system onwhich inertia forces are effective prior to unlocking of the breechbolt, have a weight of substantially 8 ounces and this may be as low assix ounces without substantial reduction in benets received from inertiaelects. The breech bolt 21 and locking block 22 have a4 weight which isdetermined by the gauge of the shotgun, typical values for aA 12 gaugegun being 7.2 ounces. Once the locking block has been disengaged fromthe barrel extension, inertia elects come into play on the entire movingsystem which has a weight of about 151/2 ounces in a 12 gauge gun.

When Ithe shotgun is tired in normal operation, the entire gun has atendency to recoil rearwardly as a result of the well-known law ofmotion .that to every action there is an equal and opposite reaction.With any human shooter, there is an initial period of substantially freerecoil consumed in the compression of the shooters clothing and thesofter layers of esh overlying the bony structure of his shoulder.During this initial period of free recoil, the entire gun mechanismacquires a substanrtial rearward velocity. `At the close of the initialperiod of free recoil, the shooters shoulder begins to resist recoilmovement with increasing force and the buttstock of the shotgun andthose parts rigidly associated therewith are decelerated. As pointed outabove, however, the breech bolt slide and parts rigidly'associatedtherewith are held in their foremost position by the action spring 33and when these parts have been moved rearwardly enough to unlock thelocking block the masses of the bolt, locking block and of the red shellare added to the relatively movable parts of the system. As a result,when the buttstock, receiver, and barrel are decelerated there is atendency for the breech slide and those parts associated therewith tocontinue in rearward motion, such motion being opposed only by theforces of friction and by the force of the action spring 33. Althoughthe force derived in this way is not sutiicient to produce completeautoloading functioning of the firearm unless excessively heavy inertiaweights are added -to the system, it does provide a substantialoperating force. The reality ofthis force may be readily demonstrated byclosing the gas ports 34 or by substituting a barrel which is notprovided with a gas pont. If, at the same time, the action spring 33 isentirely removed or replaced by a relatively light spring, the arm maybe tired in the normal manner and visual observation will show that theinertia effects have causes the breech mechanism to be unlocked andpartially opened. The eect of inertia on the functioning of the arm canbe substantially removed by holding the weapon free at arms length andfiring it in such a Way that there is no substantial opposition to freerecoil of the entire system. When so fired, it will be noted that evenin the complete absence of an action spring 33, the breech mechanismwill not be unlocked or opened as a result of firing. lt has beenobserved that the magnitude of this effect is not altogether dependenton lthe power of the shot shell load employed. In fact, the operatingforce derived from inertia is not much greater when the heavy huntingloads are tired than it is when light trap and skeet loads are red.Actually, the variable resistance at a shooters shoulder or shootingstyle causes a materially greater change in operating force derived frominertia than does a change in loading of the shot shell. In all cases oftiring from the human shoulder, the force derived from inertia is,however, a substantial and essential contribution to the operation ofthe iirearm. g

As previously noted, the balance of the power necessary to effectautoloading operation of the firearm is obtained by tapping gas from thebarrel through the gas ports 34. With a gas port area in the vicinity of.0250 square inch for a 12 gauge gun, the relationship between the exactgas port area and the operating powerderived therefrom is fairly linear.If this area is obtained with a single port, however, there is anoccasional tendency for performance to be somewhat erratic. We havefound that it is desirable to apportion this gas port area among aplurality of ports of lesser diameter, which as noted from the drawingenter the barrel at an angle to the line of projection of the shotcharge therein. Several advantages are derived from -this division ofgas port area, one being that the smaller diameter gas ports permittedthereby minimize the amount of lead, wad fragments, etc. associated withthe shot charge, which to some extent tend to pass through or tomomentarily lodge in the gas ports. It has also been established throughconsiderations of the flow of gas through orifices that when the exitchannel is narrowed the flow is slowed down over and above that whichwould be expected simply by the reduction vinj,area. `Thus, even thoughthe total gas port area is the same, `there will be less gas ilowingthrough two or three small gas ports than through one port and the flowthrough the multiple ports is much more consistent from shot to shot.

We have found that for 12 gauge shotguns a total gas port area of 0.0257square inch is near the optimum and that an area of 0.030 square inch isabout the maximum permissible. We have also found .that we get adequateuniformity and throttling of the gas flowing through the orices if thetotal area is apportioned between two or more ports. For example, eachof two gas ports having a diameter of 0.1285 inch has an area ofsubstantially 0.01297 square inch, so that two such ports have a totalarea of substantially 0.02594 square inch and have proven to be entirelysatisfactory. Further, ports of this diameter tend to be self-cleaningand are not likely -to be partially closed with carbonaceous deposit asmay be the case with substantially smaller ports. With the smaller`gauges of Shotguns where operating pressures are generally higher andthe weight of reciproeating parts to be moved are somewhat less, asmaller gas port is desirable and this smaller area can be ob tained bymoderate reductions in the diameter of the gas ports.

6 It has also been noted that the maguine cap 1l is provided with oneventing aperture 37 and with three venting apertures 38 selectively usedand through which a portion of the gases admitted to the gas operatingsystem are permitted to escape to atmosphere. The selection of whetherthe single aperture 37 or the multiple apertures.

38 are in alignment with the holes 40 is, as noted, determined by thesetting of the selector dial 39 in accordance with the power of theloads being used, multiple apertures being used for high-powered. loadssuch as the 2%" Magnum loads and the single small aperture being usedwith lower powered tield and trap loads.

The venting of the gas system presents a number of significantadvantages, one being related to the fact that moisture, debris andfouling of various sorts which might otherwise tend to condense on oraccumulate within the gas operating system will be readily dischargedthrough these apertures, and the forward return movement of the gaspiston provides a scavenging action to clean out the system. This actionprevents; the accumulation of condensed moisture which could causerusting, and the accumulation of other condensed gaseous products ofcombustion which Vcould tend to deposit solid fouling of a carbonaceousnature.

Another extremely important advantage of the vented gas system becomesapparent from theoretical consideration of the flow of gas throughthrottling orifices which establishes that the lrate of tlow throughsuch an orifice is not as dependent upon the differential pressureacross the orilice as would ordinarily be expected. In fact, in a systemof this kind it can be shown that less gas will ow through the orificeinto a system having a low pressure on the downstream side of theorifice than would ilow into a system having a higher downstreampressure which is exactly opposite to the expected effect. Venting ofthe gas system from the downstream side of the throttling orificetherefore permits:

(1) The use of orilices from the barrel of size sutilcient to ensurethat they will not become clogged, and

(2) Exerts a two-fold eiect in reducing the forces acting on the pistonby:

(a) Bleeding off gas which would exert pressure on the piston; and

(b) As a result of the decreased downstream pressure resulting from thevent, the rate of flow through the throttling orifice is also reduced.

The end result is increased reliability of performance and the decreaseof shock loads upon the gas piston, the action bars and other movableelements of the system with increased service life for all. 1

With 12 gauge, Trap, Skeet, or low base held loads a single ventingaperture .067 inch in diameter is adequate but with such high-poweredloads as the 12 gauge, 2% Magnum, it is preferable, as pointed outbefore, to utilize three venting apertures each of which may be 0.128inch in diameter. The selector dial permits the choice to be made by theshooter in accordance with the loads being used.

In order to successfully accommodate the diversity of loads with whichthe modern shotgun is faced, we have deliberately designed the gas portsand the gas vents in the magazine cap to provide so little power thatthe tirearm will not operate as an autoloader with any but the veryhigh-powered loads unless the gas operating force is augmented by theforces derived from inertia and previously discussed herein. Althoughthe operating forces derived from the two sources are additive and bothincrease with the more powerful shot shells, the net result of thiscombination of two operating forces is to impose on the mechanism shockloadings of substantially smaller magnitude than would be applied if anattempt were made to operate solely by means of power derived from thegas, as has always been the case heretofore in weapons utilizing gaspower.

As has been previously noted, the forces derived from inertia may besubstantially eliminated by n'ng the arm at arms length and so supportedas to minimize the opposition to free recoil. With the arm fired in thisway and depending for operating power solely on gas passing through thegas ports, it may be demonstrated that with the low-powered loads therewill be consistent failures to extract the red shell or to eject it fromthe receiver after tiring. When these same loads are iired from theshoulder in the normal manner, the forces derived from inertia willproduce consistent functioning with any type of shooter, whether he beone who holds his firearm loosely and shoots with a slack shoulder or insuch a way as to -roll with the recoil, or whether he be a shooter whoholds his arm rigidly and backs up the buttstock of the gun with a veryfirmly supported shoulder. With the higher powered loads enoughadditional force is derived from the gas that there will be onlyoccasional failures to extract when the gun is tired in a free recoilcondition, showing that with such loads our shotgun borders on beingfully gas-operated. In normal operation, the gun will be iired with therelatively low-powered loads with a small -venting aperture in themagazine cap and when a change is made to the relatively high-poweredshot shells, the selector will be changed to expose the multiple ventsof a larger diameter to minimize shock loads on the mechanism. Noimmediate harm, however, will result from tiring the high-powered loadswith the smaller vent aperture, since it requires an accumulation ofexcessive shock loadings to cause any appreciable damage to the workingmechanism.

For details of the novel interconnection between the action bars and thegas piston, reference may be had particularly to Figs. 2 and 3. It willbe noted that the rivet 29 is permanently attached to the ac tion barbridge 28 and that this rivet is provided with a neckeddown portionwhich passes through and is guided by the slot 30 in the wall of themagazine tube. The head 29 on the inner end ofthe rivet has a greaterdiameter than the width of the slot, so that the action bars are snuglyguided in parallelism with the magazine tube and the rivet is securelyheld in position to remain engaged Within the hole 31 in the skirt 32aof the gas piston. Disassembly of the mechanism for inspection andcleaning is permitted by the provision at one point along the slot 30 ofa disassembly notch 44 of large enough diameter to permit the passa-geof the rivet head 29. With the action bars retracted to bring the rivet29 into registry with the disassembly notch and with the barrel removedfrom the firearm, the action bars may be twisted to one side andupwardly to disengage the rivet from the gas piston `skirt and permitthe piston to be expelled by the action spring through the front ofthemagazine tube. Assembly is elr'ected in reverse order by placing the gas`piston -in the magazine tube and compressing the action spring to bringthe hole 31 into registry with the disassembly notch 44, the rivet 29being inserted therethrough and engaged within the hole 31. It may alsobe noted that the skirt 32a of the gas piston 32 is provided with apiston ring 45. The piston ring has a relatively loose t in an annulargroove in the piston and maintains an adequate gas seal with the wall ofthe magazine tube while permitting the piston itself to lit relativelyloosely therein. The piston ring also acts as an effective scraper,tending to remove any carbonaceous or other deposits which may form onthe inner wall of the magazine and tend to impede the operation of thegas piston. The piston skirt is relieved on its outer circumferenceexcept in spaced bands to minimize the area contacting the wall of themagazine tube. The combination of the scraping action of the piston ringand a looser piston litpermitted by this construction results in an armwhich may be tired for several thousands of rounds without requiring anycleaning of the gas operating system. Factors contributing tocleanliness are, of course, the small gas ports from the barrel whichreduce the amount of material permitted to 8 enter the gas piston, andthe gas venting apertures in the magazine tube cap which tend to renderthe system self-cleaning to a considerable extent. i

The function of locking the gun open after the last shot has beenremoved from the magazine and tired is performed by a lug 46 on the endof the magazine follower 6 which, without a shell in the magazine,overlies the forward end of the carrier 47. When the breech bolt slidereaches its rearward position, it engages in the usual manner with thecarrier dog 48 and, with the carrier blocked by the lug 46 the breechbolt slide is locked in this rearward position. The slide may bereleased to permit the breech to close by manually engaging thefollower- 6 through the bottom loading port and urging it back into themagazine tube suiciently to disengage the lug 46 from the. carrier.

No attempt has been made herein to describe the de tails ofthoseportions of theV mechanism which are common to one orthe other of thetwo previous patents referred to herein and, to the extent that theoperation of such mechanism is not immediately obvious from aninspection of the drawings, reference may be made to those patents tocomplete the picture. Although we have shown` and described herein onlyone specific embodiment of our invention, we do not consider'that theinvention is limited to the specific details of this disclosure. For anexact definition` of the limits which we consider applicable to ourinvention,l reference may be had to the appended claims.

We claim:

1 In an autglgadns maar@ having a barrel, a receiver; to which saidbarrel is secured, a tubular magazine se.- cured to said receiver andextending forward hfrom in parallelism with said barrel, a breech boltwithin said receiver, and locking means to releasably secure the breechbolt as a closure for the breech end of the barrel; the improvement inautoloading operating mechanism comprisingv in combination a breech boltslide longitudinally slidable in said receiver and coupled to saidbreech bolt with capacity for limited longitudinal movement with respectthereto, said slide being engageable with said locking means to unlocksame during the rearward portion of said limited longitudinal movementand to lock the same during the forward portion of said limitedlongitudinal movement, saidV slide being arranged at the rearwardextreme of said limited movement to cause the reciprocation of saidbreech bolt with the slide; a pair of` laterally spaced action barsrigidly coupled to said slide and longitudinally slidable therewith; agas cyinder formed by the forward portionV of said magazine tube and acap closing the forward end' of the same; gas port means communicatingbetween the bore of the barrel and the interior of said gas cylinder;and a gas piston reciprocable in the cylinder formed by the forward endof the magazine tube and rigidly coupled tothe forward end of both ofsaid action bars, said action bars being joined to each other at theirforward end by an integral bridge 'shaped to partially embrace theoutside of the portion of the magazine tube defining the gas cylinder,an elongated slotiormed in the side wall of said gas cylinder portion ofthe magazine tube, a lug attached to said action bar bridge andextending through said slot, said lug being formed with a head engagingthe inner wall of said cylinder at each edge of said slot, a skirt onsaid gas piston, and means defining a hole in said gas piston skirtembracing the head of said lug.

2. The combination described in claim 1, said slot being provided in alocation remote from the ends thereof with a lateral enlargement great`enough to pass the head of said lug to permit disengagement or' saidaction bars from said cylinder and said piston.

9 3. The combination described in claim 2, said lateral enlargementbeing oiset to one side of the line of said slot requiring said actionbars to be twisted laterally to that side to permit disassembly.

References Cited in the le of this patent UNITED STATES PATENTS 785,974McClean Mar. 28, 1905 10 Ballesen Feb. 1, 1944 Crockett Feb. 19, 1946Sefred Sept. 27, 1949 Benson Feb. 28, 1950 Studler Apr. 13, 1954Crittendon et a1 Aug. l0, 1954 Green Mar. 5, 1957 Simmons Dec. 3, 1957

